MQTT Notifications
The MQTT notification support is different than the other notification platforms. It is a service. This means that you don’t have to create a configuration entry but you need to provide more details when calling the service.
Call Service section from the Developer Tools allows you to send MQTT messages. Choose mqtt/publish from the list of Available services: and enter something like the sample below into the Service Data field and hit CALL SERVICE.
{"payload": "Test message from HA", "topic": "home/notification", "qos": 0, "retain": 0}
Using the REST API to send a message to a given topic.
$ curl -X POST -H "x-ha-access: YOUR_PASSWORD" \
-H "Content-Type: application/json" \
-d '{"payload": "Test message from HA", "topic": "home/notification"}' \
http://IP_ADDRESS:8123/api/services/mqtt/publish